Lots of good advice here...I used to get get really mired down in the "what ifs".what if I don't respond this time and she really needs support..what if I say the wrong thing/don't say the right thing..then I slowly grew to realize that I truly had no control .. I certainly didn't have the power to make or break her sobriety.
It is definately ok not to respond..it was just last week she stole from you..she's using and most likely she is trying a differnt tactic..mom didn't respond to my threats, so now I'll try another approach..look how good I'm doing!
In my opinion, when we step away from the drama and refuse to engage...they can feel that as a consequence of their addiction and that is always a good thing..not to punish them, but having healthy boundaries for ourselves where we get off the roller coaster and let them take the ride by themselves..